<template>
  <div class="goods-image">
    <!-- 大图 -->
    <div
    v-show='show'
      class="large"
      :style="[{ backgroundImage: `url(${images[currIndex]})`},largePosition ]"
    ></div>
    <!-- 中 图 -->
    <div class="middle" ref="target">
      <img :src="images[currIndex]" alt="" />
      <!-- 遮罩色块 -->
      <div v-show='show' class="layer" :style="layerPosition" ></div>
    </div>
    <!-- 小图 -->
    <ul class="small">
      <li
        v-for="(img, i) in images"
        :key="i"
        :class="{ active: i === currIndex }"
      >
        <img @mouseenter="currIndex = i" :src="img" alt="" />
        <!-- currIndex=i  鼠标经过将图片索引赋值给大图的src -->
      </li>
    </ul>
  </div>
</template>
<script>
import { reactive, ref, watch } from "vue";
import { useMouseInElement } from '@vueuse/core'
export default {
  name: "GoodsImage",
  props: {
    images: {
      type: Array,
      default: () => [],
    },
  },
  setup(props) {
    //   当前预览图的索引
    const currIndex = ref(0); //默认第一张

    // 1.是否显示遮罩和大图片
    const show = ref(false)  //默认看不见
    // 2.遮罩层的坐标(样式)
    const layerPosition = reactive({
        left:0,
        top:0
    })
    // 3.大图的背景定位（样式）
    const largePosition = reactive({
        backgroundPositionX:0,
        backgroundPositionY:0
    })
    // 4.使用useMouseInElement得到基于左上角的坐标和是否离开元素数据
    const target = ref(null)
    const {elementX, elementY, isOutside} = useMouseInElement(target)
    watch([elementX, elementY, isOutside],()=>{
        // 根据得到的数据设置自己的样式数据和是否显示数据
        // 当鼠标在中等盒子里面  则显示大图和遮罩 
        show.value = !isOutside.value
        // 计算坐标
        const position = {x:0,y:0}

        // x
        if(elementX.value <100) position.x = 0
        else if(elementX.value >300) position.x = 200
        else position.x = elementX.value - 100

        // y
        if(elementY.value <100) position.y = 0
        else if(elementY.value >300) position.y = 200
        else position.y = elementY.value - 100

        // 给样式赋值
        layerPosition.left = position.x + 'px'
        layerPosition.top = position.y + 'px'
        largePosition.backgroundPositionX = - 2* position.x + 'px'
        largePosition.backgroundPositionY = - 2* position.y + 'px'

    })
    return {target, currIndex ,show ,layerPosition, largePosition};
  },
};
</script>
<style scoped lang="less">
.goods-image {
  width: 480px;
  height: 400px;
  position: relative;
  display: flex;
  z-index: 500;
  .large {
    position: absolute;
    top: 0;
    left: 412px;
    width: 400px;
    height: 400px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    background-repeat: no-repeat;
    background-size: 800px 800px;
    background-color: #f8f8f8;
  }
  .middle {
    width: 400px;
    height: 400px;
    background: #f5f5f5;
    position: relative;
    cursor: move;
    .layer {
      width: 200px;
      height: 200px;
      background: rgba(0, 0, 0, 0.2);
      left: 0;
      top: 0;
      position: absolute;
    }
  }
  .small {
    width: 80px;
    li {
      width: 68px;
      height: 68px;
      margin-left: 12px;
      margin-bottom: 15px;
      cursor: pointer;
      &:hover,
      &.active {
        border: 2px solid @xtxColor;
      }
    }
  }
}
</style>